Brake Light Warning Light On (325i 88)

[Chspyder]

My 1988 325i has had a brake warning light in the information center (up between the visors) since the car was painted. The light comes on when the car goes to the second click on the ignition, then the check light (vdo) on the dash comes on, I then push the reset button on the info center, then check light goes out (the info center stays lit) then if the brakes are tapped or the left turn signal comes on the check light illumiates again. then I press reset and the check light (the info center light still stays on) goes off till the next restart.


Please help, all bulbs are good, but is their a possibility of a certain resistance bulb that is supposed to be in it, or what about the little computer board in the third brake light.


Thanks
Jt

[Antiburn]

Are you talking about the brake pad sensor light or the light that tells you that there a a bulb out?

[Chspyder]

Bulb out light.

[Antiburn]

You might need a new socket, check them all for burning marks on the metal tab. Or if you have the kind that pops directly into the light cluter you might need a new light cluster.

[jeffreyb4me]

"Chspyder" you were probably on the right track with that little pc board in the HMSL unit. They do go bad allowing the bulb to function but not give the lamp the relay a load signal so it 'thinks' the bulb is inop. I never tried fixxing one, I've always replaced them BUT do check the right & left side sockets and conductor plates in the trunk.

[Chspyder]

Checked all connection plates, all clean and tidy, it seems to be a possibility for the third brake light, but as I stated earlier the turn signal goes on it makes it act funny.

Also I almost forgot, the turn signal comes on engine off ignition on run, the gas gague will move with the blinker.

Anybody have better info and schematics than Haynes Manual

[jeffreyb4me]

you stated it was just painted, any bodywork done i.e. crash damage??....to the rear of the car??? Allllsoooo, are the left signals operating properly, brightness, speed, etc.. compared the to right side??

[beemer nut]

Replace the brake light switch. Located behind the brake pedal....

[Chspyder]

How would it be the brake light swithc?

[jeffreyb4me]

Well it actually could be, but only when first starting the car. These early systems, while 'active', only cleared and tested the check relay after depressing the rake pedal the first time. IF the switch was intermittant [burnt contacts] and not always closing, the 'BRAKE LAMP' warning would not clear and remain on until a subsequent brake application during which the switch actually functioned and 'set' the system to 'monitor mode' of 'reading' bulb operation and the 'warning' and 'Check Control' warning would only reappear if it sensed a bulb circuit problem...........until you started the car again.
Does that make sense???? I hope it explained the system a little and this MAY NOT be YOUR problem...when all else fails...........
*****ALWAYS TROUBLESHOOT USING PLAUSIBLE PERCEPTIONS*****
Stay in touch...........................jeff b.

[Chspyder]

Jeff b, you sound really technicial (and knowlegable) I am a computer tech and you have out spoke my vocabulary, I think that you said that when the system came on the brake switch fails, causeing the light to illuminate on the control panel, and it does. Then when I press the check light and the VDO warning goes off, then I press the brake pedel and the VDO check lights flashes again. I am not shure if the last part goes with what you said, if so how can I check the contacts? I am going out now to see if the brake switch is in any way not working to my eye inspection.

[jeffreyb4me]

I screwed up a simple explaination again I think with too much info......?........let's try this.

CCP = check control panel in headliner
VDO = amber triangle in cluster
LED = brake bulb warning in CCP
CCB = the test/reset button on the CCP

1] when you start the car AND do NOTHING else, the LED & VDO will be on.

2] step on the brake and both SHOULD go out, if the bulbs/circuits are good.

3] if they stay on after depressing the brake pedal,
a] there's one or more bulbs out
b] defective HMSL circuit board [sorry, HMSL=3rd brake lamp]
c] bad brake lamp switch

4] if the VDO & LED come on while driving [you've hit the brakes] it's usually due to [a] but can also be corrosion or looseness in the lamp assemblies. Pressing the CCB will turn off the VDO until the next braking event with a lamp problem, [a] or [b].

5] this system can't tell you if the brake lamp switch goes bad after you start the car.....it will have no way of knowing you've touched the brakes.......later model BMW's do [a double contact switch].

6] if all the bulbs are new and CORRECT, and the contacts are CLEAN and working BRIGHTLY [ DON'T use brake lamp bulbs for taillamps!! the lamps will melt!] the problem is the HMSL circuit board.

HOPE THIS IS CLEAR NOW.........................jeff b........................

[macalintalr]

Not sure if this is still active, but I had the same problem on my '87 325is since I bought it 2 years ago. I did all the tests and it came down to the 3rd brake light. Remove the module so you can inspect the printed circuit board (PCB) that has a copper coil soldered on it, and inside the coil, a wire goes through it. On mine, there was a "cold solder" on one of the connections of the inner wire (you would see the lead solder cracked). I just redid the solder to ensure good connectivity, and the check light behaved correctly since then! Hope this helps someone else.